Lemma 3 (Bennett's inequality [1]}) 
 Let \(Z_{1},\ldots ,Z_{n}\)  be i.i.d. random variables
with values in \([0,B]\)  and let \(\delta >0\) . Then, with probability
at least \(1-\delta \)  in \((Z_{1},\ldots ,Z_{n})\) ,
\(\text{$\mathbb {E}Z$} & \le \frac{1}{n}\sum _{i=1}^{n}Z_{i}+\sqrt{\frac{2\hat{\mathbb {V}}[Z]\ln 2/\delta }{n}}+\frac{7B\ln 2/\delta }{3(n-1)}.\) 

